Evaluation of Geranium Cultivars and Biorational Products to Control Botrytis Blight in the Greenhouse

Botrytis blight caused by the fungus Botrytis cinerea is an important disease of geranium, affecting leaves, stems, and flowers, and decreasing the crop's marketability. Our objectives were to evaluate (i) susceptibility of geranium cultivars to B. cinerea and (ii) efficacy of biorational products for control of Botrytis blight on geranium. Disease assessment included the number of blighted leaves, foliar lesions, and leaves with B. cinerea sporulation. The area under the disease progress curve (AUDPC) was calculated. Among the 10 geranium cultivars evaluated, 'Pinto Premium Orange', 'Horizon Coral Spice', and 'Ivy Tornado White' had significantly less disease than 'Ringo 2000 Violet' and 'Maverick Scarlet Picotee' for all measured parameters. When 11 treatments were compared in the efficacy trial of biorational products, Botector (Aureobasidium pullulans) and Prestop (Gliocladium catenulatum) effectively controlled the disease according to AUDPC for blighted leaves and leaves with sporulating B. cinerea in both Ringo 2000 Violet and Pinto Premium Orange. Zio (Pseudomonas chlororaphis), Serifel (Bacillus amyloliquefaciens), Serenade Opti (B. subtilis), and LifeGard (B. mycoides) were also effective when combined with the geranium cultivar Pinto Premium Orange, one of the least susceptible cultivars in our study based on AUDPC values for all measured parameters. AUDPC for leaves with sporulating B. cinerea showed that all biorational products included in the study effectively limited B. cinerea except Actinovate (Streptomyces lydicus) in Pinto Premium Orange geranium. A sustainable management approach could combine one of the least Botrytis-susceptible geranium cultivars identified with biorational controls for effective Botrytis blight control.